• Table of Contents
• Introduction
• Testing philosophy
• Unit tests
• Writing comprehensive tests
• Mocking
• Integration tests
• Unit versus integration tests at Oppia
• When to mock
• Run backend tests
• Identifying whether the tests passed
• Coverage reports
• Overall coverage
• Warning: full coverage does not mean your tests are comprehensive
• Associated test files
• Per-file coverage
• Write backend tests
• Backend test structure
• Guidelines for writing good tests
• Common testing scenarios
• Sharding backend tests
• How sharding works
• Common errors
• Adding new tests to shards
• Examples
• Example: Writing unit tests for domain classes
• Example: Writing integration tests for handlers (controllers)